Highly selective and sensitive reaction of cyanide with 2,2-dihydroxy-1,3-indanedione.

A novel reaction of cyanide with 2,2-dihydroxy-1,3-indanedione in the presence of sodium carbonate is described. It is highly selective and sensitive, and suitable for the determination of hydrogen cyanide in the environment and free cyanide ions in water, blood, urine, serum, etc. As little as 1.25x10(-7) mol x L(-1) CN(-) (3.25x10(-9) g x mL(-1) cyanide) can be determined by use of this reaction. The color system obeys Beer's law in the range 10 ng x mL(-1) to 1.0 microg x mL(-1) at 510 nm. The molar absorptivity was 8.0x10(4) L x mol(-1) x cm(-1) for a solution of concentration 0.2 microg x mL(-1). All other important analytical properties of the reaction have been studied. It is proposed that the purple color produced under these reaction conditions is that of 2-cyano-1,2,3-trihydroxy-2 H indene.